This patch provides a workaround for the errata described in GRLIB-TN-0013.
If the workaround is enabled it will:
* Prevent div and sqrt instructions in the delay slot.
* Insert NOPs to prevent the sequence (div/sqrt) -> (two or three floating
point operations or loads) -> (div/sqrt).
* Not insert NOPs if any of the floating point operations have a dependency
on the destination register of the first (div/sqrt).
* Not insert NOPs if one of the floating point operations is a (div/sqrt).
* Insert NOPs to prevent (div/sqrt) followed by a branch.
It is applicable to GR712RC, UT700, and UT699.
gcc/ChangeLog:
2017-11-17 Daniel Cederman <ceder...@gaisler.com>
* config/sparc/sparc.c (fpop_reg_depend_p): New function.
(div_sqrt_insn_p): New function.
(sparc_do_work_around_errata): Insert NOP instructions to
prevent sequences that could trigger the TN-0013 errata for
certain LEON3 processors.
(pass_work_around_errata::gate): Also test sparc_fix_tn0013.
(sparc_option_override): Set sparc_fix_tn0013 appropriately.
* config/sparc/sparc.md (fix_tn0013): New attribute.
(in_branch_delay): Prevent div and sqrt in delay slot if fix_tn0013.
* config/sparc/sparc.opt (sparc_fix_tn0013: New variable.
---
gcc/config/sparc/sparc.c | 113 ++++++++++++++++++++++++++++++++++++++++++++-
gcc/config/sparc/sparc.md | 7 +++
gcc/config/sparc/sparc.opt | 4 ++
3 files changed, 122 insertions(+), 2 deletions(-)
diff --git a/gcc/config/sparc/sparc.c b/gcc/config/sparc/sparc.c
index 401dfcb..6e91114 100644
--- a/gcc/config/sparc/sparc.c
+++ b/gcc/config/sparc/sparc.c
@@ -945,6 +945,39 @@ mem_ref (rtx x)
return NULL_RTX;
}
+/* True if any of INSN's source register(s) is REG. */
+
+static bool
+insn_uses_reg_p (rtx_insn *insn, unsigned int reg)
+{
+ extract_insn (insn);
+ return ((REG_P (recog_data.operand[1])
+ && REGNO (recog_data.operand[1]) == reg)
+ || (recog_data.n_operands == 3
+ && REG_P (recog_data.operand[2])
+ && REGNO (recog_data.operand[2]) == reg));
+}
+
+/* True if INSN is a floating-point division or square-root. */
+
+static bool
+div_sqrt_insn_p (rtx_insn *insn)
+{
+ if (GET_CODE (PATTERN (insn)) != SET)
+ return false;
+
+ switch (get_attr_type (insn))
+ {
+ case TYPE_FPDIVS:
+ case TYPE_FPSQRTS:
+ case TYPE_FPDIVD:
+ case TYPE_FPSQRTD:
+ return true;
+ default:
+ return false;
+ }
+}
+
/* True if INSN is a floating-point instruction. */
static bool
@@ -1065,6 +1098,79 @@ sparc_do_work_around_errata (void)
insert_nop = true;
}
+ /* Look for sequences that could trigger the GRLIB-TN-0013 errata. */
+ if (sparc_fix_lost_divsqrt
+ && NONJUMP_INSN_P (insn)
+ && div_sqrt_insn_p (insn))
+ {
+ int i;
+ int fp_found = 0;
+ rtx_insn *after;
+
+ const unsigned int dest_reg = REGNO (SET_DEST (single_set (insn)));
+
+ next = next_active_insn (insn);
+ if (!next)
+ break;
+
+ for (after = next, i = 0; i < 4; i++)
+ {
+ /* Count floating-point operations. */
+ if (i != 3 && fpop_insn_p (after))
+ {
+ /* If the insn uses the destination register of
+ the div/sqrt, then it cannot be problematic. */
+ if (insn_uses_reg_p (after, dest_reg))
+ break;
+ fp_found++;
+ }
+
+ /* Count floating-point loads. */
+ if (i != 3
+ && (set = single_set (after)) != NULL_RTX
+ && REG_P (SET_DEST (set))
+ && REGNO (SET_DEST (set)) > 31)
+ {
+ /* If the insn uses the destination register of
+ the div/sqrt, then it cannot be problematic. */
+ if (REGNO (SET_DEST (set)) == dest_reg)
+ break;
+ fp_found++;
+ }
+
+ /* Check if this is a problematic sequence. */
+ if (i > 1
+ && fp_found >= 2
+ && div_sqrt_insn_p (after))
+ {
+ /* If is this is the short version of the problematic
+ sequence we add two NOPs in a row to also prevent
+ the long version. */
+ if (i == 2)
+ emit_insn_before (gen_nop (), next);
+ insert_nop = true;
+ break;
+ }
+
+ /* No need to scan past a second div/sqrt. */
+ if (div_sqrt_insn_p (after))
+ break;
+
+ /* Insert NOP before branch. */
+ if (i < 3
+ && (!NONJUMP_INSN_P (after)
+ || GET_CODE (PATTERN (after)) == SEQUENCE))
+ {
+ insert_nop = true;
+ break;
+ }
+
+ after = next_active_insn (after);
+ if (!after)
+ break;
+ }
+ }
+
/* Look for either of these two sequences:
Sequence A:
@@ -1393,7 +1499,7 @@ public:
virtual bool gate (function *)
{
return sparc_fix_at697f || sparc_fix_ut699 || sparc_fix_b2bst
- || sparc_fix_gr712rc;
+ || sparc_fix_gr712rc || sparc_fix_lost_divsqrt;
}
virtual unsigned int execute (function *)
@@ -1763,9 +1869,12 @@ sparc_option_override (void)
if (!(target_flags_explicit & MASK_LRA))
target_flags |= MASK_LRA;
- /* Enable the back-to-back store errata workaround for LEON3FT. */
+ /* Enable applicable errata workarounds for LEON3FT. */
if (sparc_fix_ut699 || sparc_fix_ut700 || sparc_fix_gr712rc)
+ {
sparc_fix_b2bst = 1;
+ sparc_fix_lost_divsqrt = 1;
+ }
/* Disable FsMULd for the UT699 since it doesn't work correctly. */
if (sparc_fix_ut699)
diff --git a/gcc/config/sparc/sparc.md b/gcc/config/sparc/sparc.md
index 7e03bda..0e45509 100644
--- a/gcc/config/sparc/sparc.md
+++ b/gcc/config/sparc/sparc.md
@@ -430,6 +430,10 @@
(symbol_ref "(sparc_fix_b2bst != 0
? FIX_B2BST_TRUE : FIX_B2BST_FALSE)"))
+(define_attr "fix_lost_divsqrt" "false,true"
+ (symbol_ref "(sparc_fix_lost_divsqrt != 0
+ ? FIX_LOST_DIVSQRT_TRUE : FIX_LOST_DIVSQRT_FALSE)"))
+
(define_attr "fix_gr712rc" "false,true"
(symbol_ref "(sparc_fix_gr712rc != 0
? FIX_GR712RC_TRUE : FIX_GR712RC_FALSE)"))
@@ -581,6 +585,9 @@
(define_attr "in_branch_delay" "false,true"
(cond [(eq_attr "type"
"uncond_branch,branch,cbcond,uncond_cbcond,call,sibcall,call_no_delay_slot,multi")
(const_string "false")
+ (and (eq_attr "fix_lost_divsqrt" "true")
+ (eq_attr "type" "fpdivs,fpsqrts,fpdivd,fpsqrtd"))
+ (const_string "false")
(and (eq_attr "fix_b2bst" "true") (eq_attr "type" "store,fpstore"))
(const_string "false")
(and (eq_attr "fix_ut699" "true") (eq_attr "type" "load,sload"))
diff --git a/gcc/config/sparc/sparc.opt b/gcc/config/sparc/sparc.opt
index 22267f5..71ead75 100644
--- a/gcc/config/sparc/sparc.opt
+++ b/gcc/config/sparc/sparc.opt
@@ -253,6 +253,10 @@ Enable workarounds for the errata of the GR712RC processor.
TargetVariable
unsigned int sparc_fix_b2bst
+;; Enable workaround for GRLIB-TN-0013 errata
+TargetVariable
+unsigned int sparc_fix_lost_divsqrt
+
Mask(LONG_DOUBLE_128)
;; Use 128-bit long double
--
2.9.3
